1. Technical Field
The present invention relates to a polymerizable composition for an optical material, an optical material obtained from the polymerizable composition for an optical material, and a method for preparing the optical material.
2. Related Art
Conventionally, a plastic lens has been used as a replacement for an inorganic material in the applications of optical components. These plastic lenses are lightweight and non-brittle as compared to the inorganic materials that had been preferably used until then, and can be colored, and therefore, they have been used appropriately. Particularly, in the case of using as the optical components such as a lens, there is a demand for a plastic material having a high refractive index. As the plastic material having a high refractive index, for example, there have been suggested a sulfur-containing urethane resin (thiourethane resin) in Patent Documents 1 to 3, and an episulfide resin in Patent Document 4.
Furthermore, recently, a thinner spectacle lens has come into demand from the viewpoint of fashionability, and further, “a 2-point frame”, which a frame for supporting the spectacle lens is not provided in the fringe of the spectacle lens and the spectacle lens is supported with two holes on both ends thereof, has been used. In order to lessen the thickness of the spectacle lens, a higher refractive index of the optical material was required. Meanwhile, when the 2-point frame is used, a process for ma king two holes on both ends of the spectacle lens (“2-point process”) is carried out, and thus the spectacle lens has been required to have excellent processibility and high strength. In addition, there was a demand for a material having excellent light resistance so as to withstand outdoor use.    [Patent Document 1] Japanese Laid-open Patent Publication No. H2-270859    [Patent Document 2] Specification of Chinese Laid-open Patent Publication No. 1405198    [Patent Document 3] Japanese Laid-open Patent Publication No. H5-273401    [Patent Document 4] Japanese Laid-open Patent Publication No. H11-322930